1. Object Interaction Models - Review The use case and its scenarios serve as a vehicle for organizing the object interactions that take place. Each scenario involves a certain set of interactions. UML uses two different notations and models for object interaction diagrams: one is called sequence diagram and the other a communication diagram. The sequence diagram presents object interaction arranged in time sequence. It shows the object involved in time scenario and the sequence of message that are exchanged.

2. The communication diagram shows interaction organized around the objects and their messages to each other. These two diagram forms are interchangeable, some CASE tools will automatically generate one from the other. Which one to use is up to the developer. Object Interaction Models - Review

3. Sequence Diagram

4. Communication Diagram

5. Example objects shown as icons Arrows indicate messages Time sequence indicated by numbering the messages Communication Diagram Elements

6. Show how objects are linked Like an object diagram with the addition of messages Emphasizes context and overall organization Benefits of Communication Diagram

7. Communication Diagram

10. Soda Machine Customer inserts money and makes a selection. Console delivers information to the register Soda is in stock, register tells dispenser to deliver soda. Dispenser tells console to release soda Constructing a Communication Diagram

11. Soda Machine Customer inserts money and makes a selection. Console delivers information to the register Soda is not in stock, register tells console to display “Sold out” message. Register returns cash to console Constructing a Communication Diagram

12. Soda Machine Conditions User has input more money than the purchase price. Machine has correct change. Constructing a Communication Diagram

13. Soda Machine Conditions User has input more money than the purchase price. Machine does not have correct change. Constructing a Communication Diagram